The invention relates to a closure cap with the features of the preamble of the independent patent claims. Such closures of plastic are known in a multitude and are used for closing amongst other things also containers with carbonated beverages.
With this many various arrangements for achieving a sealing between the sealing cap and the container opening are known. With a known sealing variant the sealing is achieved by a sealing disk which is layed onto the inner side of the cap base and which by the cap base is pressed against the container opening.
It is important that above all in the region of the outer edge of the container opening, a good pressing-on of the sealing disk is achieved.
From EP 55 916 there is known such a closure. The sealing disk by way of a projection in the region between the cap base and the cap skirt is pressed against the upper outer edge of the opening of the container in a specific manner. In this manner a pressing with a high surface pressure and thus a good sealing effect is achieved.
If in the inside of the bottle there is formed an excess pressure for example by way of fermentation or heating, there exists the danger that the container breaks or that the closure cap jumps off. There have already been various attempts to solve this problem.
From EP 370 272 it is for example known to partly interrupt the circumferential rib for pressing the sealing disk. The sealing disk may in the region of the interruptions escape given an excess pressure and thus permit a reduction of the pressure in the container. The construction according to EP 370 272 is however burdened by the disadvantage that in the regions of the interruption the sealing disk may not at all be pressed onto the outer edge. This may lead to leakage even when in the container no excess pressure is to be found.
From U.S. Pat. No. 4,629,083 and from EP 770 559 there is furthermore known a closure cap in which the bulge which is to press the sealing disk against container neck is not arranged as a thickening in the transition region between the cap base and the cap skirt, but as a circumferential lip projecting axially downwards. With this design there exists the problem that the pressing on account of the gap between the rib and the inner side of the cap skirt is not very strong. These two designs likewise do not solve the problem of the bursting of the container with an increased inner pressure.
It is therefore the object of the present invention to avoid the disadvantages of the known, in particular thus to provide a closure cap which with an increased inner pressure in the container functions in the manner of a safety valve, i.e. permits a gas escape, which however reliably seals with a normal inner pressure and which is simply and economically manufacturable.
According to the invention, these objects are achieved with a closure cap comprising a cap base, a cap skirt with inner retaining elements which may be brought into engagement with outer retaining means of an opening of the container, a sealing disk which at least partly bears on the cap base, and a circumferential bulge arranged in a transition region between said cap base and said cap skirt for pressing said sealing disk onto an upper outer edge of said opening of the container. The closure gap between the bulge and the skirt at least partly may be provided with a circumferential undercut. The bulge in at least one segment-like section may have a weakening such that the weakenings facilitate relief of over-pressure within the container.
The closure cap for a container comprises a cap base and a cap skirt. The cap skirt is provided with retaining means which may be brought into engagement with outer retaining means on the opening of a container. The cap may for example also comprise a snap or bayonette thread. The cap can advantageously be applied with carbonated beverages or with beverages which are filled hot.
The closure cap furthermore comprises a sealing disk which at least partly bears on the cap base. Of course also a sealing inlay which does not pass through, for example a sealing ring is conceivable. The closure cap furthermore comprises in the transition region between the cap base and the cap skirt a circumferential bulge for pressing the sealing disk onto the upper outer edge of the opening of the container. The closure cap between the bulge and the skirt is provided at least partly with a circumferential undercut. The undercut may extend uniformly over 360 degrees over the circumference of the closure cap.
It is however also conceivable to form the undercut only in segments. The bulge is furthermore in at least one segment-shaped section provided with a weakening. The combination of a circumferential bulge with an undercut and with a weakening in segment-like sections leads to a particularly good sealing effect which however permits the venting of an excess pressure.
Because the bulge circumferentially is formed without interruptions in the transition region between the cap base and the cap skirt, a uniform pressing of the sealing disk onto the container opening is effected. The undercut gives the lower edge of the bulge a certain flexibility so that the bulge on impinging with pressure is bendable outwards. By way of the selection of the size of the undercut the pressure at which the inner pressure is vented may be exactly predetermined. The weakenings in the bulge give the bulge in the predetermined sections a larger radial flexibility. In these section the sealing disk with an inreased inner pressure may be pressed outwards. Venting is thus possible.
Preferably the undercut extends from the lower edge of the bulge into a region which has a distance to the cap base. This means that the bulge in the transition region between the cap base and the cap wall is formed continuously.
In a particularly preferred embodiment example the weakening of the bulge is formed by weakenings on the outer side of the bulge, which faces the cap skirt. With this segment-like weakenings are produced without there resulting an irregular pressing surface. The pressing surface which presses the sealing disk against the outer upper edge of the container opening thus extends over 360xc2x0 and is essentially flat, i.e. it has no deepenings or elevations. The deepenings on the outer side of the bulge however also give the bulge an increased radial flexibility in predeterminable regions.
Of course it is also conceivable to provide other types of weakenings. For example the bead may be weakened by another material selection, another orientation of the material or by another thickness of the material.
In an alternative embodiment example the weakening of the bulge is formed by weakenings which from the lower end of the bulge extend axially against the cap base and which preferably extend over the whole thickness of the bulge. Since the deepenings do not extend up to the upper end of the bulge but only towards the cap base, the disadvantages of a bulge with continuous interruptions according to the state of the art are avoided.
The weakening extends advantageously substantially over the height of the undercut. In the region between the lower end of the bulge and the end of the undercut the bulge is flexible. In this region the weakening is particularly effective.
The sections which comprises weakenings of the bulge comprise preferably as a whole (i.e. the sum of all sections together) an angular range of 90xc2x0 to 220xc2x0. With this preferably about 3 to 15 sections are provided with weakenings.
For increasing the venting function the cap base on its inner side may furthermore be provided with at least one radial deepening which extends radially over a sealing section of the cap base. The sealing section defines that zone of the cap base which presses the sealing disk against the container opening. On account of the deepening in the cap base the sealing disk may be forced axially upwards and thus form a path for reduction of an excess pressure. In a particularly preferred embodiment example the radial deepening in the radial seal is flush with a weakening of the bulge.
In a further embodiment example the cap base on its inner side is provided with a circumferential rib which runs concentrically to the closure cap. The circumferential rib serves for increasing the pressing force of the sealing disk. Furthermore also radially running ribs may be provided on the cap base. The radial ribs are preferably formed higher than the circumferential rib. In this case the radial deepenings are done away with. It has been ascertained that the provision of such radial ribs above all is advantageous with hot fillings, for example with fruit juices. On account of the heat with this the sealing disk becomes softer and there usually exists the danger that the sealing disk is pulled axially inwards. With the radial ribs and with the circumferential rib this is avoided.